Patch "net: sched: fix NULL pointer dereference when action calls some targets" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

net: sched: fix NULL pointer dereference when action calls some targets

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
net-sched-fix-null-pointer-dereference-when-action-calls-some-targets.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Xin Long <[email protected]>
Date: Fri, 18 Aug 2017 11:01:36 +0800
Subject: net: sched: fix NULL pointer dereference when action calls some targets

From: Xin Long <[email protected]>

[ Upstream commit 4f8a881acc9d1adaf1e552349a0b1df28933a04c ]

As we know in some target's checkentry it may dereference par.entryinfo to check entry stuff inside. But when sched action calls xt_check_target, par.entryinfo is set with NULL. It would cause kernel panic when calling some targets.

It can be reproduce with:

  # tc qd add dev eth1 ingress handle ffff:
  # tc filter add dev eth1 parent ffff: u32 match u32 0 0 action xt \
    -j ECN --ecn-tcp-remove

It could also crash kernel when using target CLUSTERIP or TPROXY.

By now there's no proper value for par.entryinfo in ipt_init_target, but it can not be set with NULL. This patch is to void all these panics by setting it with an ipt_entry obj with all members = 0.

Note that this issue has been there since the very beginning.

---
 net/sched/act_ipt.c |    2 ++
 1 file changed, 2 insertions(+)

@@ -34,6 +34,7 @@ static int ipt_init_target(struct xt_ent
 {
 	struct xt_tgchk_param par;
 	struct xt_target *target;
+	struct ipt_entry e = {};
 	int ret = 0;
 
 	target = xt_request_find_target(AF_INET, t->u.user.name,

@@ -44,6 +45,7 @@ static int ipt_init_target(struct xt_ent
 	t->u.kernel.target = target;
 	memset(&par, 0, sizeof(par));
 	par.table     = table;
+	par.entryinfo = &e;
 	par.target    = target;
 	par.targinfo  = t->data;
 	par.hook_mask = hook;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/net-sched-fix-null-pointer-dereference-when-action-calls-some-targets.patch queue-4.4/sctp-fully-initialize-the-ipv6-address-in-sctp_v6_to_addr.patch